High Voltage Inverting Charge Pumps Offer Low Input & Output Ripple

The negative LDO post regulator is powered from the inverting charge pump output. The positive and negative LDO output voltages can be adjusted down to 1.2V and -1.2V, respectively using external resistor dividers. Both devices operate over a wide 4.5V to 32V input voltage range.

The internal charge pump of the LTC3260 and LTC3261 function in either low quiescent current Burst Mode operation or low noise constant frequency mode at up to 88% efficiency. In Burst Mode operation the charge pump output regulates to –0.94 • VIN. Also, in Burst Mode operation the LTC3261 draws only 60μA of quiescent current, while the LTC3260 draws only 100uA with both LDOs enabled. Constant frequency operation offers low input and output ripple; in this mode the charge pump produces an output equal to –VIN and operates at a fixed 500kHz or to a programmed value between 50kHz to 500kHz using an external resistor.

Other IC features include low external parts count with ceramic capacitor stability, soft-start circuitry to prevent excessive current flow during start-up, plus short circuit and thermal protection. The LTC3260 and LTC3261 are well-suited for a variety of applications such as low noise bipolar/inverting supplies from a high voltage input, industrial/instrumentation low noise bias generators, portable medical equipment and automotive infotainment systems.

The LTC3260 is available in a low-profile (0.75mm) 3mm x 4mm 14-lead DFN package and a 16-lead MSOP package, both with a backside thermal pad. The LTC3261 is available in a 12-lead MSOP package with backside thermal pad. For both devices, the E- and I-grade operating junction temperature is -40°C to +125°C. 1000-piece pricing for the E grade starts at $3.40 each for the LTC3260 and $2.87 each for the LTC3261. Both devices are available from stock.